logger.rb

class MyClass
  def initialize; end

  def log(level, msg)
    puts "#{level}: #{msg}"
  end

  [:debug, :info].each do |m|
    define_method(m) do |msg|
     log(__method__, msg)
    end
  end
  # same code for warn, error, fatal, unknown
end

MyClass.new.debug "foo"
MyClass.new.info "bar"